Refinement of Climate-, Depth-, and Time-Based Laboratory Aging Procedure for Asphalt Mixtures

Abstract

This paper refines the oxidation kinetics-based approach originally proposed in the NCHRP 09-54 project to determine the laboratory aging durations at 95°C that best reflect the effects of time, climate, and depth on loose asphalt mixtures. Aging durations that match the field aging at various pavement depths were determined in this study for asphalt mixtures, including warm-mix asphalt (WMA), polymer-modified asphalt (PMA), and reclaimed asphalt pavement (RAP). Here, the laboratory aging durations were used to calibrate a climatic aging index to prescribe the laboratory aging duration, given hourly pavement temperature history obtained from Enhanced Integrated Climatic Model analysis of the Modern Era Retrospective-Analysis for Research and Applications, Version 2 weather data. The recalibrated procedure determines the required laboratory aging durations with reasonable accuracy for virgin hot-mix asphalt (HMA) and WMA mixtures. From the recalibrated results, no variations were found with regard to the laboratory aging durations for WMA materials compared with HMA materials, but there were differences between the RAP and non-RAP mixtures. In some instances, the short-term aged RAP mixtures that were prepared according to AASHTO R 30 exceeded the aging level of 4-year-old field cores, suggesting that refinement of this standard short-term aging procedure may be necessary. Approximately half of the PMA sections evaluated exhibited outlier behavior that could have been caused by the unrealistically harsh thermal history of the field projects from which the cores were acquired.

Impacts of Field and Laboratory Long-Term Aging on Asphalt Binders

“…The degree ( n ) was determined using the “elbow” method. Plotting the goodness of fit (1–R 2 ) versus the polynomial degree ( n ), the optimum degree to the fit was determined at the “elbow” of the curve. The “elbow” of such a curve indicates when the incremental fit gain starts to decrease with increasing complexity.…”

“…The current SuperPave performance grading (PG) system uses a standard aging method, 20 h conditioning in a pressure-aging vessel (PAV) to represent long-term aging. Given that aging severity is location dependent, the 20 h PAV conditioning represents varied service lives for different locations and may not represent long-term effects ( 1 , 2 ). Extended-aging durations of 40 h, 60 h, and 80 h of PAV to replace the current binder aging protocol used in SuperPave PG specifications (20 h PAV) have been explored as alternatives to long-term aging by several researchers ( 3 , 4 ).…”

“…The extent of aging depends on climatic exposure, asphalt concrete (AC) field density, depth, and binder chemistry ( 12 – 22 ). Studies on quantifying the effects of field aging are limited and region-specific ( 1 , 2 , 17–19 ). Quantifying the extent of in-service asphalt binder aging is challenging because of the inherent variability of AC, the presence of recycled asphalt pavement (RAP)/reclaimed asphalt shingles (RAS), maintenance and rehabilitation interventions, and lack of information about the asphalt binders used at the time of construction or rehabilitation.…”

Albedo Change Mechanism of Asphalt Concrete Surfaces

“…The I-FIT FI results are shown in Table 6 and illustrate a decrease in FI with increasing conditioning time and temperature, that is, increased aging. FI values in this range had been found for stiff, brittle mixes placed in Illinois (18). As of 2021, new AC mixes are required to exceed an FI of 8.0 in the unaged condition (24).…”

“…The logarithm of the magnitude of the complex modulus of the asphalt binder measured at 64°C and 10 rad/s ( log | G * | ) has been shown to be a good indicator of aging, reflecting changes in the chemical and rheological properties of the asphalt binder ( 18 ). The control and laboratory-aged asphalt binders were characterized using a Kinexus KNX2712 dynamic shear rheometer (DSR) to measure log | G * | at 64°C and 10 rad/s.…”